Ok, my 305 is giving me the following problems:
1. It guzzles gas like crazy
2. the exhaust smells funky
3.the check engine light keeps coming on during my commute at the same time everyday

my best guess is that the O2 sensor is shot
I've had the computer checked for codes but nothing shows up

 

Sounds like a condition where you are running rich. Maybe you have a bad connection somewhere or a bad wire between the ECM and the o2 sensor. Not sure, but i think that would trigger the check engine light. Dont kow if it would pull codes or not. Sounds like your ecm THINKS its running lean, when in reality its not. This would make the ECM add more fuel. And if the ECM adds more fuel to a car thats already running a proper ratio, this would make it run rich. ANd i know running rich can emit a strong smell. It would also cause fuel economy to drop. But like i said, i dont know if a bad connector/wire would trigger the check engine light without setting a code. Have you tried jumping the upper right 2 terminals (i think those are the 2) with a paper clip? i think it flashes the code then.

 

If the check engine light is coming on, then it has a code. AFAIK, after you ground the proper connectors on the ALDL connector terminal, you should flash code 12 three times then any trouble codes should flash.

If not, then there's your problem, not the O2 sensor.